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Current process corrections typically are done based on feedback per lot and per exposure chuck. Wafers exposed on the same chuck, belonging to the same lot get exactly the same process corrections. In current HVM processing however, an important contribution to the wafer variation is the differences in processing of the individual wafers. These differences can be related to variations in the usage of the processing tools (e.g. different etch chambers). An extension of the process corrections from chuck-based to process-context based can help in reducing the systematic wafer-level variation. With Integrated Metrology the sampling of wafers through the lot can be adjusted to make sure all different processing-contexts are covered in the measurements. Finally, the impact on Litho process cycle time of the total metrology effort required to enable these performance improvements, will be evaluated, and a proposal will be made on the optimum strategy to enable high-volume manufacturing. |
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Semiconducting wafers
Metrology
Principal component analysis
Overlay metrology
Optical alignment
Immersion lithography
Scanners
